1. Field of the Invention
The present invention relates to a PC card which is inserted into a card slot of a personal computer, for example, in order to extend the functions of the personal computer.
2. Description of the Related Art
In general, a personal computer is made up mainly of a computer body having an operation function, a memory function, and the like, a key board for inputting a signal to the computer body, a memory including a floppy disk and the like for storing memory in the computer body, and a display for indicating a program, an operational result, and the like.
Furthermore, the personal computer is provided with a card slot into which a PC card can be additionally attached in order to extend the memory contained in the computer body, add a modem, provide an IDE interface with an external CD-ROM drive and a hard disk, and the like. The size and shape of the PC card is specified by PC Card Standard and Standard by JEIDA (Japan Electric Industry Development Association).
For personal computers, a 32-bit byte has been gradually employed instead of a 16-bit byte in order to enhance processing speeds. Accordingly, there are two types of PC cards having respective sizes and shapes, that is, 16-bit PC cards and 32-bit PC cards. Similarly, card slots on the personal computer side are roughly divided into two groups, that is, 16-bit and 32-bit card slots.
Further, with respect to personal computers, in order to reduce the consumption electric power, the driving voltage for the computer body has been changed from 5.0 V to 3.3 V. For ordinary uses, the driving voltage for 16-bit PC cards is set at 5.0 V, while that for 32-bit PC cards at 3.3 V. Since the driving voltage has been reduced from 5.0 V to 3.3 V, the 32-bit PC card and the card slot are provided with ground electrodes for reinforcing the grounding, in order to secure the transmission or reception of a signal between the PC card and the personal computer.
The PC card is provided with a card key groove formed on the left side viewed in the card insertion direction, so that the PC card can be prevented from being improperly inserted, turned inside out, and can be distinguished between 16-bit and 32-bit PC card types. The card-side key groove of the 16-bit PC card is wider than that of the 32-bit PC card.
With this difference between the card-side key groove widths, the 16-bit PC card can be inserted into the 16-bit card slot and also into the 32-bit card slot. On the other hand, the 32-bit PC card can only be inserted into the 32-bit card slot, and is prevented from being inserted into the 16-bit card slot. As a result, the respective protuberances of the ground electrode provided for the card slot of the 32-bit PC card are prevented from being inserted into the 16-bit card slot which has no parts for receiving the protuberance. This protects the ground electrode, the card insertion hole of the card slot, and the like.
A 32-bit PC card of the above-described type is disclosed in Japanese Unexamined Patent Publication No. 9-58163, and is publicly known.
The PC card produced according to the above-described conventional technology includes a frame of which one end functions as a connector-attachment port and accommodates a circuit board inside thereof. Two panels form lids at the opposite sides of the frame and a connector is disposed in the connector attachment port of the frame for connecting the circuit board to the personal computer. A ground electrode is provided between one of the two panels and the connector for connecting the ground of the circuit board to the ground of the personal computer.
Further, one of the two panels is perforated to provide plural protuberance-receiving holes in the position corresponding to the connector attachment port. The ground electrode is composed of a flat plate elongated in the connector-lengthwise direction and protuberances are formed on the flat plate and project through the respective protuberance-receiving holes.
The above-described conventional 16-bit PC card is provided with the card-side key groove having a different size from that of the 32-bit PC card so that it can be distinguished from the 32-bit PC card, and moreover, the 32-bit PC card can be prevented from being inserted into the 16-bit card slot, as described above.
On the other hand, users require PC cards which are available as both the 16-bit and 32-bit cards. For the purpose of meeting this requirement, it is necessary to provide a PC card which can be inserted into either of the 16-bit and 32-bit card slots, irrespective of the shapes and sizes of the card slots of personal computers.